Angular mirror.



O. VON HOPE. ANGULAR MIRROR. APPLIOA TION FILED O 0T. 12, 1911.

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COLUMBIA PLANODRAPH 60., WASHINGTON. D. c.

Patented May 28, 1912;

UNITED STATES PATENT Mormon.

CHRISTIAN voN HOEE, OFWILMERSDO'RF, NEAR BERLIN, GERMANY, ASSIGNOR TO THE FIRM F OPTISCHE ANSTAL'I G. P. NEAR BERLIN, GERMANY.

GOERZ AKTIENGESELLSCI-IAET, 0F lERIIilDENA'U;

AN GUIIAR MIRROR.

Patented May 28,1912. Serial No. 654,357.

To all whom it may concern Be it known that I, CHRISTIAN VON Horn, a citizen of the German Empire, and resident of Wilmersdorf, near Berlin, Germany,

have invented certain new and useful Imwhereby invariability of the angle inclosed by the mirror surfaces is insured. According to the invention this object is attained in forming the angular mirror body of a separate support with reflectors attached thereto, and in using for the support a material whereof the thermic expansion coefficient is approximately zero, with reflectors of a different coeflicient of expansion arranged thereon in such manner that they can move relatively to the support, parallel with their reflective surfaces. In this manner the angle inclosed by the reflectors is kept perfectly constant by means of the nonexpanding support, without occurrence of strains in the reflectors, due to the difference in the coefiicients of expansion. As material for the reflector support nickel-steel alloy is suitable, containing about 36.1% of nickel. A convenient and cheap form of support is obtained by using a yoke of nickel-steel, with its limbs adjusted so that their lateral edges inclose the angle which is to be the angle of the mirror.

The connection of the support to the reflectors is with advantage made by making the reflectors abut against the support at three points, and pressingthem againstthe support at these points.

One form of construction of the improved angular mirror is shown in the accompanyin drawing, in which- Tigure 1 shows the angular mirror in cross section; Fig. 2 shows the same in side view, and Fig. 3 shows the nickel-steel blank out of which the yoke shaped support for the reflectors is made.

The two lateral limbs of the yoke-shaped support for the reflectors are marked 1.

These limbs are connected by a bridge 2.

The lateral edges 3 of the limbs inclose the angle which the mirror is to have. Each reflector 4 rests at three points 5 on the sup port. A three armed spring 6 serves to press each reflector against the support at the abutment points 5. The springs 6. are acted on by springs 7, which are fixed at "S to the bridge connecting the limbs 1. Pins 9 on the limbs project into recesses 10 in the reflectors and limit in a suitable degree the freedom of movement of the reflectors on the support.

The new angular mirror is designed for use in telescopic instruments such as base l1ne telemeters where it is essential that the rays entering the instrument are deviated by reflecting devices through definiteangles which remain unaltered independently from variations of temperature which the instrument may undergo.

What I claim is:

1. An angular'mirror, comprising a support, consisting of a material whereof the thermic expansion coefficient is approximately zero, and reflectors of different expansion coeflicient mounted on said support in such manner that they can move relatively to the support, parallel with their reflecting surfaces.

2. An angular mirror, comprising a yokeshaped reflector support of nickel-steel alloy whereof the limbs are adjusted so that their lateral edges inclose the angle required for the angular mirror, and reflectors mounted on the lateral edges of said yoke limbs in such a manner that they can move relatively to their support parallel with their reflecting surfaces.

3. An angular mirror, comprising a support, consisting of a material whereof the thermic expansion coeflicient is approximately zero, reflectors mounted thereon, three abutment points on said support for each reflector and pressure exerting, means adapted to press the reflectors against the abutment points, the reflectors being free to move relatively to their support parallel with their reflecting surfaces.

4. An angular mirror, comprising a support, consisting of a material whereof the thermic expansion coefficient is approximately zero, reflectors mounted thereon, In testimony whereof I have signed this three abutment polnts on sa1d support for specification 1n the presence of two subscribeach reflector and sprlngs mounted on the 1ng Witnesses.

reflector support adapted to press the re- CHRISTIAN VON HOF E. 5 flectors against their abutment points, said Witnesses:

pressure springs having their contacting HENRY HAsPER,

points in line with the abutment points. VVOLDEMAR HAUPT.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

